The present disclosure is generally related to phase change inks. More specifically, the present disclosure is directed to hot melt or phase change inks containing specific colorant compounds. One embodiment of the present disclosure is directed to a phase change ink carrier and a compound of the formula

wherein R1, R2, R3, and R4 each, independently of the others, is (i) a hydrogen atom, (ii) an alkyl group, (iii) an aryl group, (iv) an arylalkyl group, or (v) an alkylaryl group, wherein R1 and R2 can be joined together to form a ring, wherein R3 and R4 can be joined together to form a ring, and wherein R1, R2, R3, and R4 can each be joined to a phenyl ring in the central structure; wherein a and b each, independently of the others, is an integer which is 0, 1, 2, or 3; wherein R3 and R6 are each optionally present and wherein each of R3 and R6 independently of the other, if present, are independently selected from (i) an alkyl group, (ii) an, aryl group, (iii) an arylalkyl group, (iv) an alkylaryl group, (v) a halogen atom, (vi) an ester group, (vii) an amide group, (viii) a sulfone group, (ix) an amine group or ammonium group, (x) a nitrile group, (xi) a nitro group, (xii) a hydroxy group, (xiii) a cyano group, (xiv) a pyridine or pyridinium group, (xv) an ether group, (xvi) an aldehyde group, (xvii) a ketone group, (xviii) a carbonyl group, (xix) a thiocarbonyl group, (xx) a sulfate group, (xxi), a sulfide group, (xxii) a sulfoxide group, (xxiii) a phosphine or phosphonium group, (xxiv) a phosphate group, (xxv) a mercapto group, (xxvi) a nitroso group, (xxvii) an acyl group, (xxviii) an acid anhydride group, (xxix) an azide group, (xxx) an azo group, (xxxi) a cyanato group, (xxxii) an isocyanato group, (xxxiii) a thiocyanato group, (xxxiv) an isothiocyanato group, (xxxv) a urethane group, or (xxxvi) a urea group, wherein R5 and R6 can each be joined to a phenyl ring in the central structure, wherein

wherein R8, R9, and R10 each, independently of the other, is optionally present and wherein, if one or more are present, each of R8, R9, and R10 is independently selected from (i) a hydrogen atom, (ii) an alkyl group, (iii) an aryl group, (iv) an arylalkyl group, or (v) an alkylaryl group; wherein in further embodiments, the number of carbon atoms in R1+R2+R3+R4+R5+R6+R8+R9+R10 is at least about 4, or in another embodiment at least about 16; wherein R″ is optionally present and wherein R′ and R″, if present, are each independently selected from (i) an alkyl group, (ii) an aryl group, (iii) an arylalkyl group, or (iv) an alkylaryl group, wherein R′ or R″ are independently selected from linear or branched, saturated or unsaturated, or cyclic components, wherein in embodiments, R′ or R″, if present, are independently selected from an alkyl group containing from about 0 carbon atoms (that is, R″ is 0) to about 8 carbon atoms, from about 1 carbon atom to about 8 carbon atoms, or about 12 carbon atoms, or about 18 carbon atoms, or about 30 carbon atoms, or about 50 carbon atoms, or about 100 carbon atoms, wherein in embodiments, R′ or R″, if present, are independently selected from an aryl group containing about 5 carbon atoms, or about 6 carbon atoms, or about 10 carbon atoms, wherein in embodiments R′ or R″, if present, are independently an alkylaryl group or an arylalkyl group containing about 7 carbon atoms, or about 30 carbon atoms, or about 50 carbon atoms; or about 100 carbon atoms, wherein in one embodiment, R′ contains about 18 carbon atoms and R″ is 0 carbon atoms; wherein A is an anion, and wherein CA is either a hydrogen atom or a cation.
In general, phase change inks (sometimes referred to as “hot melt inks”) are in the solid phase at ambient temperature, but exist in the liquid phase at the elevated operating temperature of an ink jet printing device. At the jet operating temperature, droplets of liquid ink are ejected from the printing device and, when the ink droplets contact the surface of the recording substrate, either directly or via an intermediate heated transfer belt or drum, they quickly solidify to form a predetermined pattern of solidified ink drops. Phase change inks have also been used in other printing technologies, such as gravure printing, as disclosed in, for example, U.S. Pat. No. 5,496,879 and German Patent Publications DE 4205636AL and DE 4205713AL, the disclosures of each of which are totally incorporated herein by reference.
Phase change inks for color printing typically comprise a phase change ink carrier composition which is combined with a phase change ink compatible colorant. In a specific embodiment, a series of colored phase change inks can be formed by combining ink carrier compositions with compatible subtractive primary colorants. The subtractive primary colored phase change inks can comprise four component dyes, namely, cyan, magenta, yellow and black, although the inks are not limited to these four colors. These subtractive primary colored inks can be formed by using a single dye or a mixture of dyes. For example, magenta can be obtained by using a mixture of Solvent Red Dyes or a composite black can be obtained by mixing several dyes. U.S. Pat. No. 4,889,560, U.S. Pat. No. 4,889,761, and U.S. Pat. No. 5,372,852, the disclosures of each of which are totally incorporated herein by reference, teach that the subtractive primary colorants employed can comprise dyes from the classes of Color Index (C.I.) Solvent Dyes, Disperse Dyes, modified Acid and Direct Dyes, and Basic Dyes. The colorants can also include pigments, as disclosed in, for example, U.S. Pat. No. 5,221,335, the disclosure of which is totally incorporated herein by reference. U.S. Pat. No. 5,621,022, the disclosure of which is totally incorporated herein by reference, discloses the use of a specific class of polymeric dyes in phase change ink compositions.
Phase change inks have also been used for applications such as postal marking, industrial marking, and labeling. Phase change inks are desirable for ink jet printers because they remain in a solid phase at room temperature during shipping, long term storage, and the like. In addition, the problems associated with nozzle clogging as a result of ink evaporation with liquid ink jet inks are largely eliminated, thereby improving the reliability of the ink jet printing. Further, in phase change ink jet printers wherein the ink droplets are applied directly onto the final recording substrate (for example, paper, transparency material, and the like), the droplets solidify immediately upon contact with the substrate, so that migration of ink along the printing medium is prevented and dot quality is improved.
Compositions suitable for use as phase change ink carrier compositions are known. Some representative examples of references disclosing such materials include U.S. Pat. No. 3,653,932, U.S. Pat. No. 4,390,369, U.S. Pat. No. 4,484,948, U.S. Pat. No. 4,684,956, U.S. Pat. No. 4,851,045, U.S. Pat. No. 4,889,560, U.S. Pat. No. 5,006,170, U.S. Pat. No. 5,151,120, U.S. Pat. No. 5,372,852, U.S. Pat. No. 5,496,879, European Patent Publication 0187352, European Patent Publication 0206286, German Patent Publication DE 4205636AL, German Patent Publication DE 4205713AL, and PCT Patent Application WO 94/04619, the disclosures of each of which are totally incorporated herein by reference. Suitable carrier materials can include paraffins, microcrystalline waxes, polyethylene waxes, ester waxes, fatty acids and other waxy materials, fatty amide containing materials, sulfonamide materials, resinous materials made from different natural sources (tall oil rosins and rosin esters, for example), and many synthetic resins, oligomers, polymers, and copolymers.
British Patent Publication GB 2 311 075 (Gregory et al.), the disclosure of which is totally incorporated herein by reference, discloses a compound of the formula

wherein X1 is an ester group or an amide group (such as of a carboxylic or sulfonic acid) or a fatty amine salt of a sulfonic acid, each X2 independently is a substituent, m has a value of from 0 to 2, Y1 and Y2 are each independently H, alkyl, or halo, each Z independently is an ester or amide group, and A- is an anion. The compound is useful as a colorant for toners, D2T2 printing, plastics, polyesters, nylons, and inks, especially ink jet or hot melt inks.
U.S. Pat. No. 1,991,482 (Allemann), the disclosure of which is totally incorporated herein by reference, discloses a process of producing rhodamine dyes which comprises condensing a halogenated primary amine of the benzene series with fluorescein dichloride and sulfonating the condensed product. U.S. Pat. No. 5,013,857 (Berneth et al.), the disclosure of which is totally incorporated herein by reference, discloses a process for the preparation of sulpho-free triphenyl-methane dyestuffs. U.S. Pat. No. 5,847,162 (Lee et al.), the disclosure of which is totally incorporated herein by reference, discloses a class of 4,7-dichlororhodamine compounds useful as fluorescent dyes having the structure

wherein R1-R6 are hydrogen, fluorine, chlorine, lower alkyl lower alkene, lower alkyne, sulfonate, sulfone, amino, amido, nitrile, lower alkoxy, lining group, or combinations thereof or, when taken together, R1 and R6 is benzo, or, when taken together, R4 and R5 is benzo; Y1-Y4 are hydrogen or lower alkyl or, when taken together, Y1 and R2 is propano and Y2 and R1 is propano, or, when taken together, Y3 and R3 is propano and Y4 and R4 is propano; and X1-X3 taken separately are selected from the group consisting of hydrogen, chlorine, fluorine, lower alkyl carboxylate, sulfonic acid, —CH2OH, and linking group. In another aspect, the disclosure includes reagents labeled with the 4,7-dichlororhodamine dye compounds, including deoxynucleotides, dideoxynucleotides, and polynucleotides. In an additional aspect, the disclosure includes methods utilizing such dye compounds and reagents including dideoxy polynucleotide sequencing and fragment analysis methods. U.S. Pat. No. 4,935,059 (Mayer et al.), the disclosure of which is totally incorporated herein by reference, discloses basic rhodamine dyes suitable for use in recording fluids for the ink jet process and for coloring paper stock having the formula

where L is C2-C10-alkylene, R1, R2, and R3 are each independently of the others hydrogen, substituted or unsubstituted C1-C10-alkyl or C5-C7-cycloalkyl or R1 and R2 together with the nitrogen atom linking them together are a hetero cyclic radical, An- is one equivalent of an anion and m and n are each independently of the other 0 or 1. U.S. Pat. No. 4,647,675 (Mayer et. al.), the disclosure of which is totally incorporated herein by reference, discloses compounds of the general formula

where A- is an anion, R is hydrogen or unsubstituted or substituted alkyl or cycloalkyl, R1 and R2 independently of one another are each hydrogen or unsubstituted or substituted alkyl or cycloalkyl, or one of the radicals may furthermore be aryl, or R1 and R2, together with the nitrogen atom, form a saturated heterocyclic structure, the radicals R3 independently of one another are each hydrogen or C1-C4-alkyl, R4 and R5 independently of one another are each unsubstituted or substituted alkyl or cycloalkyl, or one of the radicals may furthermore be hydrogen, aryl or hetaryl, R4 and R5, together with the nitrogen atom, form a saturated heterocyclic structure, n is 1, 2 or 3, X is hydrogen, chlorine, bromine, C1-C4 alkyl, C1-C4-alkoxy or nitro and Y is hydrogen or chlorine, are particularly useful for dyeing paper stocks. U.S. Pat. No. 1,981,515 (Kyrides), the disclosure of which is totally incorporated herein by reference, discloses intermediates for rhodamine dyestuffs. U.S. Pat. No. 1,981,516 (Kyrides), the disclosure of which is totally incorporated herein by reference, discloses intermediates for secondary alkylated rhodamine dyes. British Patent Publication GB 421 737, the disclosure of which is totally incorporated herein by reference, discloses dyes of the rhodamine series, which are prepared by condensing naphthalene-2:3-dicarboxylic acid with a m-aminophenol in which the nitrogen group is substituted by one or two alkyl groups, the products, if desired, being sulphonated. The unsulphonated products may be used as lake colouring matters whilst the sulphonated dyes are acid wool dyes. In examples, (1) naphthalene-2:3-dicarboxylic acid is condensed with diethyl-m-aminophenol in the presence of zinc chloride giving a product which dyes tannin-mordanted cotton in the same shade as Rhodamine B and a sulphonated product which dyes wool bluish-red shades; (2) monoethyl-m-aminophenol is used instead of the diethyl-m-aminophenol in example (1), yielding a dye, which when sulphonated dyes wool red-orange shades; (3) 2-ethylamino-p-cresol replaces the diethyl-m-aminophenol in example (1), yielding a dye dyeing and printing tannin-mordanted cotton in shades similar to Rhodamine 69BS and when sulphonated dyeing wool red. Japanese Patent Publication JP 61221265, the disclosure of which is totally incorporated herein by reference, discloses rhodamine compounds of formula I

wherein R1, R3 are each lower alkyl; R2 is lower alkyl, 10 C or higher long-chain alkyl; R4 is 10 C or higher long-chain alkyl; X— is an anion, or squarylium compounds of formula II

wherein R2 is 10 C or higher long-chain alkyl. Example: 3,6-(N,N′diethyl-N,N′-dioctadecyl)diamino-9-(2-carboxyphenyl)xanthilium perchlorate Use: materials for molecular electronics, which are suitable for use as materials for photoelectric converter, optical memory, etc. Preparation: 2-(4-N,N′-diethylamino-2-hydroxybenzoyl)-benzoic acid, which is a condensate between N-ethyl-N-octadecyl-m-hydroxyaniline and phthalic anhydride, is reacted with N-ethyl-N-octadecyl-m-hydroxyaniline to obtain the compound of formula I. 3-HOC6H4N(Et)(CH2)17Me and phthalic anhydride were heated at 150° for 4 hours, treated with aqueous NH3, and the amorphous intermediate mixed with aqueous HClO4 forming a compound of formula I (R═R2=Et; R1═R3═C18H37; X═ClO4), having λmax (MeOH) 550 nm. U.S. Pat. No. 5,084,099 (Jaeger et al.), the disclosure of which is totally incorporated herein by reference, discloses modified phase change ink compatible colorants which comprise a phase change ink soluble complex of (a) a tertiary alkyl primary amine and (b) dye chromophores, i.e., materials that absorb light in the visible wavelength region to produce color having at least one pendant acid functional group in the free acid form (not the salt of that acid). These modified colorants are extremely useful in producing phase change inks when combined with a phase change ink carrier, even though the unmodified dye chromophores have limited solubility in the phase change ink carrier. Thin films of uniform thickness of the subject phase change ink compositions which employ the modified phase change ink colorants exhibit a high degree of lightness and chroma. The primary amine-dye chromophore complexes are soluble in the phase change ink carrier and exhibit excellent thermal stability. U.S. Pat. No. 5,507,864 (Jaeger et al.), the disclosure of which is totally incorporated herein by reference, discloses a phase change ink composition that includes a combination of different dye types such as an anthraquinone dye and a xanthene dye, which is most preferably a rhodamine dye. While each dye type is insufficiently soluble with respect to favored carrier compositions to preserve color saturation in reduced ink quantity prints, the dye type combination permits increased dye loading and maintains print quality. In a preferred embodiment of the disclosure, a favored carrier composition is adjusted to promote the colored form of a preferred rhodamine dye (C.I. Solvent Red 49) and mixed with a preferred anthraquinone dye (C.I. Solvent Red 172) whose concentration is kept below a critical level to prevent post printed blooming. The resulting preferred phase change ink compositions provide a magenta phase change ink with enhanced light fastness and color saturation, as well as good compatibility with preferred existing subtractive primary color phase change inks. U.S. Pat. No. 5,621,022 (Jaeger et al.), the disclosure of which is totally incorporated herein by reference, discloses a phase change ink composition wherein the ink composition utilizes polymeric dyes in combination with a selected phase change ink carrier composition. U.S. Pat. No. 5,747,554 (Sacripante et al.), the disclosure of which is totally incorporated herein by reference, discloses an ink composition comprising a polyesterified-dye (I) or polyurethane-dye (II) with a viscosity of from about 3 centipoise to about 20 centipoise at a temperature of from about 125° C. to about 165° C. and represented by the formulas

wherein A is an organic chromophore, Y is an oxyalkylene or poly(oxyalkylene), R is an arylene or alkylene, n represents the number of repeating segments, and is an integer of from about 2 to about 50, and p represents the number of chains per chromophore and is an integer of from about 1 to about 6. U.S. Pat. No. 5,902,841 (Jaeger et al.), the disclosure of which is totally incorporated herein by reference, discloses a phase change ink composition wherein the ink composition utilizes colorant in combination with a selected phase change ink carrier composition containing at least one hydroxy-functional fatty amide compound. European Patent Publication 0565798 (Shustack), the disclosure of which is totally incorporated herein by reference, discloses ultraviolet radiation-curable primary and secondary coating compositions for optical fibers. The primary coatings comprise a hydrocarbon polyol-based reactively terminated aliphatic urethane oligomer, a hydrocarbon monomer terminated with at least one end group capable of reacting with the terminus of the oligomer; and an optional photoinitiator. The secondary coatings comprise a polyester and/or polyether-based aliphatic urethane reactively terminated oligomer; a hydrocarbonaceous viscosity-adjusting component capable of reacting with the reactive terminus of (I); and an optional photoinitiator. Also disclosed are optical fibers coated with the secondary coating alone or with the primary and secondary coatings of the disclosure. U.S. patent application Ser. No. 10/607,382, filed Jun. 26, 2003, published Jan. 20, 2005, of Jeffrey H. Banning et al., and U.S. Pat. No. 6,860,931 of Jeffrey H. Banning et al., the disclosures of each of which are totally incorporated by reference herein, disclose in embodiments compounds of the formulae

wherein R1, R2, R3, and R4 each, independently of the others, is (i) a hydrogen atom, (ii) an alkyl group, (iii) an aryl group, (iv) an arylalkyl group, or (v) an alkylaryl group, wherein R1 and R2 can be joined together to form a ring, wherein R3 and R4 can be joined together to form a ring, and wherein R1, R2, R3, and R4 can each be joined to a phenyl ring in the central structure, a and b each, independently of the others, is an integer which is 0, 1, 2, or 3, c is an integer which is 0, 1, 2, 3, or 4, each R5, R6, and R7, independently of the others, is (i) an alkyl group, (ii) an aryl group, (iii) an arylalkyl group, (iv) an alkylaryl group, (v) a halogen atom, (vi) an ester group, (vii) an amide group, (viii) a sulfone group, (ix) an amine group or ammonium group, (x) a nitrile group, (xi) a nitro group, (xii) a hydroxy group, (xiii) a cyano group, (xiv) a pyridine or pyridinium group, (xv) an ether group, (xvi) an aldehyde group, (xvii) a ketone group, (xviii) a carbonyl group, (xix) a thiocarbonyl group, (xx) a sulfate group, (xxi) a sulfide group, (xxii) a sulfoxide group, (xxiii) a phosphine or phosphonium group, (xxiv) a phosphate group, (xxv) a mercapto group, (xxvi) a nitroso group, (xxvii) an acyl group, (xxviii) an acid anhydride group, (xxix) an azide group, (xxx) an azo group, (xxxi) a cyanato group, (xxxii) an isocyanato group, (xxxiii) a thiocyanato group, (xxxiv) an isothiocyanato group, (xxxv) a urethane group, or (xxxvi) a urea group, wherein R5, R6, and R7 can each be jointed to a phenyl ring in the central structure.

R8, R9, and R10 each, independently of the others, is (i) a hydrogen atom, (ii) an alkyl group, (iii) an aryl group, (iv) an arylalkyl group, or (v) an alkylaryl group, provided that the number of carbon atoms in R1+R2+R3+R4+R5+R6+R7+R8+R9+R10 is at least about 16, each Q, independently of the others, is a COOH group or a SO3H group, each Q-, independently of the others, is a COO— group or a SO3- group, d is an integer which is 1, 2, 3, 4, or 5, A is an anion, and CA is either a hydrogen atom or a cation associated with all but one of the Q- groups, provided that when

at least one of the following of (a), (b), and (c) is true: (a) the number of carbon atoms in R1+R2+R3+R4 is at least about 42, (b) at least one of R1, R2, R3, and R4 is a group of the formula

wherein R41 and R42 each, independently of the other, is an alkyl group, an aryl group, an arylalkyl group, or an alkylaryl group, or (c) at least one of R1, R2, R3, and R4 is a branched alkyl group having at least about 19 carbon atoms.
While known compositions and processes are suitable for their intended purposes, a need remains for new magenta colorant compositions. In addition, a need remains for magenta colorant compositions particularly suitable for use in phase change inks. Further, a need remains for magenta colorants with desirable thermal stability. Additionally, a need remains for magenta colorants that exhibit minimal undesirable discoloration when exposed to elevated temperatures. There is also a need for magenta colorants that exhibit a desirable brilliance. In addition, there is a need for magenta colorants that exhibit a desirable hue. Further, there is a need for magenta colorants that are of desirable chroma. Additionally, there is a need for magenta colorants that have desirably high lightfastness characteristics. A need also remains for magenta colorants that have a desirably pleasing color. In addition, a need remains for magenta colorants that exhibit desirable solubility characteristics in phase change ink carrier compositions. Further, a need remains for magenta colorants that enable phase change inks to be jetted at temperatures of over 135° C. while maintaining thermal stability. Further, a need remains for magenta colorants for use in solid ink printers that operate with lower print head temperatures much lower than 135° C. as well as in ultraviolet radiation curable systems. Additionally, a need remains for magenta colorants that enable phase change inks that generate images with low pile height. There is also a need for magenta colorants that enable phase change inks that generate images that approach lithographic thin image quality. In addition, there is a need for magenta colorants that exhibit oxidative stability. Further, there is a need for magenta colorants that do not precipitate from phase change ink carriers. Additionally, there is a need for magenta colorants that do not, when included in phase change inks, diffuse into adjacently printed inks of different colors. A need also remains for magenta colorants that do not leach from media such as phase change ink carriers into tap adhesives, paper, or the like. In addition, a need remains for magenta colorants that, when incorporated into phase change inks, do not lead to clogging of a phase change ink jet printhead. Further, there is a need for magenta colorants that enable phase change inks that generate images with sharp edges that remain sharp over time. Additionally, there is a need for magenta colorants that enable phase change inks that generate images which retain their high image quality in warm climates. Further, there is a need for magenta colorants that enable phase change inks that generate images of desirably high optical density. Additionally, there is a need for magenta colorants that, because of their good solubility in phase change ink carriers, enable the generation of images of low pile height without the loss of desirably high optical density. A need also remains for magenta colorants that enable cost-effective inks. The appropriate components and process aspects of the each of the foregoing may be selected for the present disclosure in embodiments thereof.